The OP is located in the substance of the peroneus longus tendon at the level of the calcaneocuboid joint and is ossified in approximately 20% of patients.1 Patients with painful os peroneum syndrome (POPS) present with plantar/lateral foot pain, localized along the course of the peroneus longus. Pathology may involve the OP (fracture or diastasis of multipartite OP), the peroneus longus tendon (tenosynovitis or tendon tear), or a large peroneal tubercle, which entraps the peroneus longus or OP during motion.2

Initial radiographs may demonstrate fragmentation, fracture or proximal retraction of the OP. Further evaluation with MR is often performed, which may demonstrate marrow edema within the OP (with or without a discrete fracture line). Additional findings often include tendinosis, tenosynovitis, or tearing of the peroneus longus tendon.

Treatment for POPS begins with conservative management and may progress to surgical excision of the OP. Repair, debridement or tenodesis of the peroneus longus tendon may also be required.